<template>
  <div class="pagination">
    <button :disabled="pageNo == 1" @click="pageNo -= 1">上一页</button>
    <!-- 前面 -->
    <button v-if="startNumAndEndNum.start > 1" @click="pageNo = 1">1</button>
    <button v-if="startNumAndEndNum.start > 2">···</button>

    <!-- 中间 -->
    <button @click="pageNo = page" :class="{active:page==pageNo}" v-for="(page,index) in startNumAndEndNum.end" :key="index" v-if="page >= startNumAndEndNum.start">{{page}}</button>
    

    <!-- 下面 -->
    <button v-if="startNumAndEndNum.end <= totalPage-2 ">···</button>
    <button v-if="startNumAndEndNum.end < totalPage " @click="changePage(totalPage)">{{ totalPage }}</button>
    <button :disabled="pageNo == totalPage" @click="changePage(pageNo + 1)">下一页</button>
    <button style="margin-left: 30px">共 {{ total }} 条</button>
    <div >{{startNumAndEndNum.start}} ----{{ pageNo }}----- {{ startNumAndEndNum.end }} </div>
  </div>
</template>

<script>
export default {
  name: "testPagination",
  data() {
    return {
      pageNo:30,
      pageSize:3,
      continues:5,
      total: 100,
    };
  },
  computed:{
    // 总页数
    totalPage(){
      return Math.ceil(this.total / this.pageSize)
    },
    startNumAndEndNum(){
      let start = 0, end = 0
      let {pageNo,pageSize,continues,totalPage} = this
      // 不正常现象（显示页面数大于总页数）
      if(continues > totalPage){
        start = 1
        end = totalPage
      }else{
        // 正常显现
        start = pageNo - parseInt(continues / 2)
        end = pageNo + parseInt(continues / 2)
        if(start < 1){
          start = 1
          end = continues
        }
        if(end > totalPage){
          end = totalPage
          start = totalPage - continues
        }
      }
      // if(pageNo <= 3){
      //   start = 1
      //   end = 5
      // }
      return {start,end}
    }
  },
  methods:{
    changePage(page){
      this.pageNo = page
    }
  }
};
</script>

<style lang="less" scoped>

.pagination {
  text-align: center;
  .active{
    background: #409eff !important;
  }
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #409eff;
      color: #fff;
    }
  }
}
</style>